1. Field of the Invention
The present invention relates to a method for preparing nylon 6 fibers. In particular, the invention involves the preparation of nylon 6 copolymer containing dimeric acid.
2. Description of the Related Art
Nylon fiber is widely used in the manufacture of clothing, textile and other materials. In order to expand various uses of nylon products or to enhance specific characteristicss of the products, there has been extensive research in the modification of nylon fibers. For the copolymerization method for nylon, specific comonomers are usually added to nylon copolymers. While production costs are relatively high, and development time is also prolonged, this is still the direction in which most research is focused because of the distinct characteristics of the products.
Recently, there have been many reports on changing dyeing property, moisture absorbtion, hydrophobic property, control of melting point and contractibility for modifying nylon copolymers. U.S. Pat. No. 5,194,578 discloses adding 2-methyl-pentadiamine (MPMD) to the monomers of nylon 66, followed by copolymerization to obtain nylon 66 with improved moisture absorbtion, dyeing property, spinning property and fiber contractbility.
In the current trend for processes more environmental friendly, the use of natural plants as materials for monomers has been well valued. Among these, the most famous is dimeric acid, such as dimmer linoleic acid or dimeric fatty acid etc. These are carboxyl compounds extracted naturally from beans. After certain chemical processes or reactions, aliphatic dimeric compounds containing 30xcx9c40 carbon numbers are obtained. This compound contains sidechains (carbon number is 9xcx9c20). Therefore, they can be used as comonomers to modify nylon polymer. Earlier examples are disclosed in Hungarian Patent HU 8322 (1974), which teaches the addition of dimeric acid comonomer to nylon 6, followed by copolymerization to obtain a nylon 6 copolymer having low melting point. In recent years, Monsanto Co. teaches in U.S. Pat. Nos. 4,219,459 and 4,219,460, formulations used as hot melt adhesive.
Examples of polymer containing both comonomers of 2-methyl-pentadiamine (MPMD) and dimeric acid are disclosed in U.S. Pat. Nos. 5,162,490 and 4,032,549, JP Patent No. 5311099 and WO 9601866 etc. These patents mainly involve the use of polymer as ink or coating. However, both melting points of the copolymer (less than 150) and molecular weight (MW less than 10000) are very low.
In order to overcome the above problems, an object of the invention is to provide a novel nylon copolymer and a method for preparing the same. The nylon copolymer contains 2-methyl-pentadiamine (MPMD) and dimeric acid monomers, and it exhibits high melting point and molecular weight.
In order to achieve the above objects, there is provided a method for preparing nylon 6 copolymers containing 2-methyl-pentadiamine (MPMD) and dimeric acid as monomers. The method comprises steps of polymerizing 80.0xcx9c99.9 mole % of caprolactam, 0.1xcx9c4.0 mole % of dimeric acid and 0.1xcx9c4.0 mole % of 2-methyl-1,5-pentadiamine. The polymerization temperature is preferred at 200xcx9c280xc2x0 C.
According to the method provided in the invention, the nylon 6 copolymer containing dimeric acid and 2-methyl-pentadiamine (MPMD) exhibits molecular weight greater than 20000 and melting point greater than 160xc2x0 C.
A nylon 6 copolymer exhibiting even higher molecular weight (MW greater than 30000) and melting point ( greater than 190xc2x0 C.) can be obtained when the amount of caprolactam is 90.0xcx9c99.9 mol %, dimeric acid is 0.1xcx9c2.0 mol %, and 2-methyl-pentadiamine (MPMD) is 0.1xcx9c2.0 mol %.
Solvent can be added as well, such as m-cresol.
The invention also provides a method for preparing nylon 66 polymer containing both dimeric acid and 2-methyl-pentadiamine as comonomers. The method involves the reaction of 60.0xcx9c90 mol % of hexadiacid and hexadiamine, 0.1xcx9c4.0 mol % of dimeric acid and 0.1xcx9c4.0 mol % of 2-methyl-1,5-pentadiamine in a polymerization reaction at 200xcx9c280xc2x0 C. The melting point of the obtained copolymer is greater than 160xc2x0 C. and the molecular weight is greater than 20000.
A nylon 66 copolymer exhibiting even greater molecular weight (MW greater than 30000) and melting point ( greater than 190xc2x0 C.) can be obtained when the amount of adipic acid and hexadiamine are 90.0xcx9c99.9 mol %, dimeric acid is 0.1xcx9c2.0 mol %, and 2-methyl-pentadiamine (MPMD) is 0.1xcx9c2.0 mol %.
According to the method provided in the invention, nylon 6 polymer and nylon 66 polymer containing both dimeric acid and 2-methyl-pentadiamine (MPMD) comonomers are obtained. The nylon polymers exhibit high melting points and high molecular weights. In addition, using natural plant extracts as the material, the method provided in the invention is more environmentally friendly than conventional methods.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings, given by way of illustration only and thus not intended to be limitative of the present invention.